1. Field of the Invention
The present invention generally relates to a translucent surface (such as a milled acrylic plate) that projects a desired image when light passes through it, as well as to techniques for designing such a surface. More specifically, the present invention relates to techniques for determining a surface pattern that will cast caustics which generate a recognizable image on a projection surface.
2. Description of the Related Art
In optics, a caustic refers to an envelope of light rays reflected or refracted by a curved surface, as well as to the projection of such light rays onto another surface. More specially, a caustic is the curve or surface tangent to each light ray, defining a boundary of an envelope of rays as a curve of concentrated light. For example, light passing through the curved surface of a wine glass creates a cusp-like pattern on a table which the wine glass is resting. Note, caustics are different from projecting light through a slide, as light is redirected (whether reflected or refracted) rather than absorbed, maintaining higher light levels and contrast.
One known application of reflective caustic design is luminaire design—the creation of lamp reflectors that create a desired radiance distribution for a given light source position. Other applications include e.g., in architecture (pattern glass that casts attractive caustics into a room) or designing security features which create hard-to-forge artifacts that can be “read out” under normal light.